Washington -LRB- CNN -RRB- -- A Georgetown University student was charged on Friday with possessing ricin after admitting he made the poison in his campus dorm room , a court document showed .

Daniel Harry Milzman , 19 , appeared in federal court , where a judge ordered him held pending a hearing next week .

Milzman was arrested by the FBI and charged with possessing a biological toxin , according to an FBI affidavit .

That submission said he learned how to make ricin on his iPhone and then bought ingredients at retail stores .

Ricin is a deadly toxin derived from castor beans that has no known antidote .

On Monday , Milzman allegedly showed a bag that he claimed to contain ricin to his dorm adviser , who notified school authorities . They in turn called police , the filing states .

Preliminary lab tests confirmed the substance was ricin , it said .

Milzman allegedly produced the substance a month earlier in his room , placed it in plastic bags sealed with hockey tape and stored it in his room , according to the document .

The amount produced possibly could have been enough to kill someone had it been inhaled or injected , the affidavit said .

Milzman is due back in court on Tuesday

His attorney , Danny Onorato , declined comment when contacted by CNN on Friday evening .

Georgetown said in a statement on Wednesday that tests on McCarthy Hall for the presence of biological agents were negative , and there had been no reports of anyone being exposed to ricin .

The university on Friday said the undergraduate student will not be permitted to return to campus at this time .

`` The possession or manufacturing of illegal substances are issues we take very seriously and are violations of the university 's student code of conduct , '' said media relations director Rachel Pugh in a statement .

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CNN 's Greg Seaby contributed to this report .

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Student said he made ricin , FBI affidavit says

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Daniel H. Milzman , 19 , ordered held until next hearing

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Substance could have potentially killed had it been inhaled or injected , court document says

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Georgetown checks out dorm and campus is safe ; no one has reported exposure to ricin